Sim Earth is great. It's underrated because: 1) for a SCD, it's not visually impressive, 2) the computer interface doesn't translate well to a control pad, 3) it came out kind of a late (SNES already had Sim Earth and Sim City), 4) it hasn't aged as well as Sim City, 5) the save file eats a whole memory bank.
I still love it.